Crankcase ventilation

ABSTRACT

The crankcase for an internal combustion engine is vented to the fuel-air inlet induction passage via a ventilation valve comprising a one-piece molded inner tubular valve housing member of resilient material having a downstream end adjustably telescoped into the upstream end of an outer tubular valve housing member. The outer member has a comparatively small metering orifice which cooperates with a valve element movable within the housing members in response to decreasing pressure in the induction conduit to restrict the orifice. A coil biasing spring within the inner member has an upstream end seated against a downstream facing shoulder of the valve element to oppose the latter&#39;&#39;s downstream movement. An enlarged downstream coil of the spring is confined within an interior spring retaining enlargement of the inner tubular member adjacent the latter&#39;&#39;s downstream opening and is insertable, as is also the valve element, through said downstream opening prior to telescoping of the inner member into the outer member. A plurality of endwise opening slits in the inner member at the region of the interior enlargement enable expansion of said downstream opening for insertion of the enlarged spring coil into the enlargement. After the insertion, the resilient material of the inner member returns the expanded downstream opening to its unexpanded condition, whereupon the assembly of the inner member with the valve element and biasing spring confined therein is adjustably telescoped into the outer member. An integral annular backfire control valve seat at the upstream end of the inner member defines a second orifice smaller than said downstream opening and adapted to be closed by an upstream backfire valve portion of the valve element when the latter moves upstream into seating engagement with the valve seat.

United States Patent Ohar et'al.

[ 51 May 16, 1972 [54] CRANKCASE VENTILATION [72] Inventors: Wasyl Ohar, Ann Arbor; Elmer L. McIntire, Northville, both of Mich.

Chrysler Corporation, Highland Park, Mich.

[22] Filed: Jan. 13,197]

21 Appl.No.: 106,067

[73] Assignee:

Primary Examiner-Harold W. Weakley Attorney--Talburtt and Baldwin 57 ABSTRACT The crankcase for an internal combustion engine is vented to the fuel-air inlet induction passage via a ventilation valve comprising a one-piece molded inner tubular valve housing member of resilient material having a downstream end adjustably telescoped into the upstream end of an outer tubular valve housing member. The outer member has a comparatively small metering orifice which cooperates with a valve element movable within the housing members in response to decreasing pressure in the induction conduit to restrict the orifice. A coil biasing spring within the inner member has an upstream end seated against a downstream facing shoulder of the valve element to oppose the latters downstream movement. An enlarged downstream coil of the spring is confined within an interior spring retaining enlargement of the inner tubular member adjacent the latters downstream opening and is insertable, as is also the valve element, through said downstream opening prior to telescoping of the inner member into the outer member. A plurality of endwise opening slits in the inner member at the region of the interior enlargement enable expansion of said downstream opening for insertion of the enlarged spring coil into the enlargement. After the insertion, the resilient material of the inner member returns the expanded downstream opening to its unexpanded condition, whereupon the assembly of the inner member with the valve element and biasing spring confined therein is adjustably telescoped into the outer member. An integral annular backfire control valve seat at the upstream end of the inner member defines a second orifice smaller than said downstream opening and adapted to be closed by an upstream backfire valve portion of the valve element when the latter moves upstream into seating engagement with the valve seat.

7 Claims, 4 Drawing Figures PATENTEUIAY 16 an 3, 662,724

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ZAE EL TMW CRANKCASE VENTILATION BACKGROUND AND SUMMARY OF THE INVENTION This application relates to improvements in a crankcase ventilating valve of the general type disclosed in copending application Ser. No. 40,013, filed May 25, 1970, and application Ser. No. 88,730 filed Nov. 12, 1970, and in the following representative U.S. Pats. for regulating the flow of gases from the crankcase of an internal combustion engine to-the latters air inlet system: 2,359,485; 2,716,398; 2,742,057; 3,105,477; 3,241,534; 3,263,699; 3,354,898 and 3,359,960.

In order to reduce the emission of unburned hydrocarbons from the fuel and exhaust systems of an automobile, it is customary to vent the fuel tank and carburetor bowl to the crankcase for storing fuel vapors therein when the engine is not operating, and to ventilate the crankcase during engine operation by controlled conduction of the crankcase gases comprising a mixture of fresh air and engine blow-by products into the usual carburetor inlet induction conduit to supply a portion of the combustion supporting air to the inlet fuel. The carburetor is accordingly adjusted so that when the crankcase gases are added to the customary throttle controlled fueland air supply, the desired fuel-air ratio for efficient engine operation will result. It is therefore necessary to control the ventilation flow of crankcase gases closely, otherwise inemcient engine operation and the exhausting of excessive incompletely burned fuel will result.

It has been common to provide a pressure responsive flow control valve in the ventilating conduit between the crankcase and induction conduit for controlling the ventilation flow in accordance with the engine operation. Such valves have been costly heretofore because of the close tolerances required for the component parts and the high rate of rejection of assembled valves that do not meet the required standards.

An important object of the present invention is to provide an improved crankcase ventilation valve of the foregoing character that can be economically manufactured by conventional low cost methods, as for example by molding operations, wherein the valve parts may be readily assembled and adjusted either during or after assembly to compensate for comparatively large dimensional variations in the parts and to avoid the scrapping of costly valve assemblies, yet still meet the exacting standards required for satisfactory engineoperation and exhaust emission control.

Another and more specific object is to provide such a valve comprising a tubular L-shaped body containing a metering orifice upstream of the elbow or bend of the L-body and having a tubular extension or spring retainer adjustably telescoped into its upstream end. A valve element movable within the housing is responsive to the pressure differential across the orifice for opening or restricting the latter. A coil biasing spring under compression between the valve element and the adjustable retainer or extension opposes movement of the valve element in the direction of orifice closing and urges movement of the valve element in the opposite direction to enable increased flow of crankcase gases during part throttle acceleration as the pressure in the carburetor induction conduit increases.

In the above regard the upstream end of the tubular valve housing comprising the tubular extension is connected to the crankcase. The downstream end of the housing is connected to the carburetor inlet induction conduit at a location downstream of theusual throttle valve and is thus subject to low induction pressure urging the valve element in the closing direction in opposition to the biasing spring. In the event of an engine backfire, the valve element will be blown upstream to cause an upstream backfire valve portion of the valve element to seat at an integral annular backfire valve seat of the spring retainer and close the valve.

In order to assure standardized operation of the valve, the biasing spring must be in fixed spatial relationship with respect to the adjustable retainer at all operating positions of the valve element and is provided with a downstream end enlarged with respect to the remainder of the spring within the retainer and secured within a spring retaining enlargement of the interior of the retainer adjacent the latters downstream end.

Another specific object is to provide such a valve wherein the tubular spring retainer comprises a one-piece molded structure having the integral annular backfire valve seat at its upstream end and havinga cylindrical interior downstream of the latter valve seat. The valve element and valve biasing spring are insertable into the cylindrical interior of the retainer through the latters downstream opening prior to telescoping of the retainer into the outer tubular housing. member. The upstream end of the valve element comprises the backfire valve portion adapted to seat at the backfire valve seat. The downstream end of the valve element comprises a metering portion movable within the metering orifice to control gas flow therethrough. Between the backfire valve portion and the metering portion of the valve element is a spring retaining shoulder having the upstream end of the biasing spring seated thereon. The latter comprises a cylindrical helix having its major portion coiled around the valve element and movable freely within the cylindrical interior of the retainer. The cylindrical or coil diameter of the springs downstream coil is oversize with respect to the downstream opening of the retainer and is confined within an interior annular groove which defines said spring retaining enlargement in the retainer.

A plurality of endwise opening slits are provided in the downstream end of the retainer, such that prior to telescoping of the latter into the outer housing member, the downstream portions of the retainer between the slits may be flexed outwardly at the region of the groove for insertion of the oversize biasing spring coil into the groove. Upon release of said downstream end portions to the unflexed condition, the enlarged coil will be closely confined with the spring retaining groove. Thereafter the assembly of the retainer with the valve element and biasing spring therein is adjustably telescoped into the upstream end of the outer tubular valve housing member to the desired position for proper valve operation.

Other objects of this invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

FIG. 1 is a longitudinal sectional view of a crankcase ventilation valve embodying the invention, taken in the direction of the arrows substantially along the line l-l' of FIG. 2.

FIG. 2 is a transverse sectional view taken in the direction of the arrows substantially along the line 2-2 of FIG. 1.

FIG. 3 is a fragmentary sectional view through the spring retainer prior to its assembly with the downstream tubular housing member, taken in the direction of the arrows substantially along the line 3--3 of FIG. 2 and showing the downstream end of the spring retainer expanded by a tool, and also showing the valve element and biasing springbeing assembled with the retainer via the latters downstream opening.

FIG. 4 is a view similar to FIG. 3, showing a later stage in the assembly.

It is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being prac ticed or carried out in various ways. Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS drical arm 14 enlarged at an intermediate region to provide an annular shoulder 15. Upstream of the elbow 11 is an integral coaxial metering orifice 16.

Telescoped within the upstream end of the housing member or arm 14 is a coaxial tubular molded valve housing member or spring retainer 17 having an annular interior spring retaining groove or enlargement 18 at its upper end. The groove 18 provides a seat for the upper enlarged coil 19 of a biasing spring 20 which seats at its lower end at an annular seat 21 comprising an enlargement of an axially movable valve element 22. The element 22 has a tapered downstream metering portion 23 which terminates upwardly in a cylindrical extension 24 of reduced diameter. The major portion of the spring 20 comprises a cylindrical helix extending freely around the valve element 22 and freely within the cylindrical interior of the upstream housing member 17. Thus when the automobile engine is not operating, the valve element 22 may seat by gravity at an annular conical valve seat 25 integral with the upstream end of the member 17 and defining a second orifice 26 of reduced diameter with respect to orifice 16. Exteriorily of seat 25 is a thickened region 27 comprising an annular retainer for a flexible hose.

Upstream of the spring seat 21, the valve 22 is rounded spherically at 28 to seat at the annular seat 25 and close the opening 26 upon downward movement of the valve 22, thereby to prevent a reverse flow of gases in the event of engine backfire for example. Also extending coaxially with the valve 22 through an opening in the sidewall of the housing at the region of the elbow 11 is a movement limiting the plunger 29 adjusted as described below.

During normal engine operation, combustion blow-by products comprising a mixture of air, inert gases, and incompletely burned hydrocarbons leak past the engine pistons into the crankcase, which is normally maintained at or close to atmospheric pressure by means of a fresh air vent. The upstream end of member 17 is connected with the crankcase by a hose secured at 27. The downstream end of member 12 is similarly connected with the carburetor fuel-air inlet conduit by a hose secured at 13. The blow-by gases from the crankcase flow in the direction of the arrows 30 through the valve of FIG. 1 in controlled amounts to the carburetor induction conduit in accordance with customary practice. Radial chattering of the valve element 22 during operation is minimized by means of three equally spaced fins 31 integral with the element 22 and having radial outer edges comprising continuations of the cylindrical outer surface of the valve 22 to fit closely within the orifice 16.

In order to obtain efiicient engine operation during all operating conditions, it is essential to control the crankcase recirculating flow within comparatively narrow limits, so that the flow from the crankcase when admixed with the fuel and air supplied via the carburetor will result in the desired combustible mixture for efficient engine operation with a minimum of unburned hydrocarbons in the exhaust. During engine idling when the air flow through the conduit is a minimum, the variations in the crankcase ventilating flow must be narrowly limited because small changes in the ventilating flow will amount to a large percentage change in the idle fuel-air ratio. Accordingly the adjusted positions of the plunger 29 and of the upstream housing member 17 telescoped into the housing downstream member 14 are accurately predetermined as described in the aforesaid copending application Ser. No. 40,0l3.

In order to obtain predetermined rates of gas flow for any given pressure differential across the metering orifice 16, it is also essential to maintain a predetermined spatial relationship between the biasing spring and the valve element 22, as is accomplished by means of the downstream oversize coil 19 of the spring 20 positively secured within the groove 18. Assembly of the coil 19 of oversize coil diameter within the groove 18 is accomplished by means of a plurality of endwise opening slits 32 uniformly spaced circumferentially and extending axially in the downstream end of the inner tubular member 17.

Prior to telescoping the member 17 into the outer tubular member 14, the valve element 22 with the coil spring 20 therearound as shown are inserted into the upper or downstream opening of the member 17, which opening is expanded as illustrated in FIG. 3 by means of a tool having an annularly arranged cam 33 engageable with the interior surfaces of each of the downstream end portions 34 located between the slits 32 of member 17. The cam 33 tapers conically at the lower end of a vertically reciprocable tubular plunger 35 adapted interiorly to receive the large coil 19 snugly therein, so as to frictionally retain the same, and to move downwardly coaxially around valve 22 to engage the interior of the portions 34 and flex the same outwardly to enable upstream movement of coil 19 into alignment with groove 18, FIG. 3. A second plunger 36 movable coaxially within cam plunger 35 has a lower annular seat 37 engageable with coil 19 to force the latter downwardly and out of the lower end of cam 33, FIG. 4, into alignment with groove 18. Substantially simultaneously, cam plunger 35 will be elevated to enable the portions 34 to return to their unflexed positions of FIG. 1, whereupon plunger 36 will also be elevated. The coil 19 will then be confined within groove 18 against axial movement and the major portion of reduced coil diameter of spring 20 integral with coil 19 will effect a predetermined biasing action on valve element 22 to yieldingly resist its downstream movement. The member 17 containing element 23 and spring 20 is then telescoped into the upstream end of member 14 to a desired position of adjustment.

In the above regard, the interior of member 14 and the exterior of member 17 are closely fitting cylindrical surfaces to prevent gas leakage during operation. Also, the material of member 17 will preferably be sufficiently resilient to enable its deformation as illustrated in FIG. 3 without exceeding its elastic limit. If flexing of the portions 34 to a lesser extent than illustrated in FIG. 3 is desired, the interior diameter of tubular plunger 35 may be slightly less than illustrated and the coil 19 will then be contracted slightly therein to a reduced coil diameter. In such a case, the portions 34 need not be flexed outwardly to the full extent illustrated in FIG. 3. Upon downward movement of plunger 36 against coil 19 as described above to force the coil 19 out of plunger 35 and into alignment with the groove or interior enlargement 18, the coil 19 will return to its uncontracted shape and expand into the groove 18 as above described.

Any proportioning of the two procedures, i.e. radial outward flexing of the portions 34 or radial contraction of the coil diameter of coil 19, may be employed to assemble the coil 19 within groove 18 prior to telescoping of member 17 into member 14. Because it is desirable to maintain a tight engagement between the member 17 and coil 19 within the groove 18, care must be exercised not to contract the coil diameter to such an extent that the coil 19 will be permanently deformed and fail to snugly fit within groove 18. For this reason, assembly of coil 19 within groove 18 is preferably accomplished primarily or solely by outward flexing of the portions 34.

We claim:

1. In a crankcase ventilating device for controlling the flow of gases from the crankcase to the fuel-air inlet induction conduit of an internal combustion engine to effect a predetermined low rate of flow when a predetermined large pressure differential exists between said crankcase and conduit corresponding to engine operation approximating idle conditions and to effect an increasing rate of flow when said pressure differential decreases with increasing engine load, the combination of A. a tubular valve housing comprising inner and outer tubular members having a gas passage extending therethrough and opening at upstream and downstream ends respectively adapted for connection with said crankcase and conduit respectively,

B. said outer member defining a metering orifice comprising part of said passage,

C. said inner member comprising a spring retainer of resilient material having I. a downstream end telescoped into the upstream end of said outer member,

2. means effective before said inner member is telescoped into said outer member to permit radially outwardly resilient flexing of the downstream end portions of said inner member around the downstream opening defined thereby to expand said downstream opening to receive therethrough resilient means oversize with respect thereto, comprising a plurality of peripherally spaced and axially extending endwise opening slits in said downstream end of said inner member,

an enlargement, with respect to its unexpanded downstream opening of its interior passage, at the region of said slits, and a backfire control valve seat defining a second orifice smaller than said unexpanded downstream opening and comprising a part of said passage upstream of said slits,

D. valve means in said passage having 1. a downstream metering portion movable in the downstream direction to restrict said metering orifice, and

2. an upstream backfire valve portion oversize with respect to said second orifice and movable in the upstream direction into seating engagement with said backfire control valve seat to close said passage,

E. resilient means within said inner member for yieldingly opposing downstream movement of said valve means havmg I. one end seated on said valve means, and 2. a second end oversize with respect to said unexpanded downstream opening of said inner member confined within said enlargement of the interior thereof to maintain a predetermined spatial relationship between said resilient means and inner member for all positions of said valve means.

2. In a device according to claim 1, said inner member comprising an integral molded structure having a uniform interior cores section downstream of said second orifice except at said enlargement, said enlargement comprising an interior groove in said slit end, and said resilient means comprising acoil spring having a major portion freely movable axially within said inner member, said second end comprising an oversize coil of said spring adapted to pass through said downstream end upon outward flexing of said downstream end portions and dimensioned to fit snugly within said groove when said downstream end portions are unflexed.

3. In the combination according to claim 2, said valve means having a shoulder downstream of said backfire valve portion thereof, said one end of said coil spring comprising the latters upstream coil seated on said shoulder, said oversize coil comprising the downstream coil of said coil spring.

4. In a crankcase ventilating device for controlling the flow of gases from the crankcase to the fuel-air inlet induction conduit of an internal combustion engine to effect a predetermined low rate of flow when a predetermined large'pressure differential exists between said crankcase and conduit corresponding to engine operation approximating idle conditions and to effect an increasing rate of flow when said pressure differential decreases with increasing engine load, the combination of A. a tubular valve housing comprising inner and outer tubular members having a gas passage extending therethrough and opening at upstream and downstream ends respectively adapted for connection with said crankcase and conduit respectively,

B. said outer member defining a metering orifice comprising part of said passage,

C. said inner member comprising a spring retainer having 1. a downstream end telescoped into the upstream end of said outer member,

2. means effective before said inner member is telescoped into said outer member to facilitate insertion of oversize resilient means into said inner member through the latters downstream opening comprising a plurality of peripherally spaced and axially extending endwise opening slits in said downstream end of said inner member,

3. an enlargement with respect to said downstream opening of its interior passage at the region of said slits, and

4. a backfire control valve seat defining a second orifice smaller than said downstream opening and comprising a part of said passage upstream of said slits,

D. valve means in said passage having 1. a downstream metering portion movable in the downstream direction to restrict said metering orifice, and

2. an upstream backfire valve portion oversize with respect to said second orifice and movable in the upstream direction into seating engagement with said backfire control valve seat to close said passage,

E. resilient means within said inner member for yieldingly opposing downstream movement of said valve means havmg 1. one end seated on said valve means, and 2. a second end oversize with respect to said downstream opening of said inner member confined within saidenlargement of the interior thereof to maintain a predetermined spatial relationship between said resilient means and inner member for all positions of said valve means.

5. In the combination according to claim 4, said inner member comprising an integral molded structure having a uniform interior cross section downstream of said second orifice except at said enlargement, said enlargement comprising an interior groove in said slit end, and said resilient means comprising a coil spring having a major portion freely movable axially within said inner member, said second end comprising an oversize coil of said spring dimensioned to fit snugly within said groove.

6. In the method of making a crankcase ventilating device for controlling the flow of gases from the crankcase to the fuel-air inlet induction conduit of an internal combustion engine to eifect a predetermined low rate of flow when a predetermined large pressure differential exists between said crankcase and conduit corresponding to engine operation approximating idle conditions and to effect an increasing rate of flow when said pressure differential decreases with engine load, the steps of I A. providing an outer tubular valve housing member having 1. a downstream end adapted for connection with said conduit,

2. a metering orifice intermediate its ends, and

3. an upstream end portion of cylindrical interior section,

B. providing an inner tubular valve housing member having 1. an upstream end adapted for connection with said crankcase,

2. a downstream end portion of cylindrical exterior section adapted to telescope snugly into said upstream end portion of cylindrical section,

3. a plurality of peripherally spaced and axially extending endwise opening slits in said downstream end portion to enable radial outward flexing of the downstream end portions between said slits to expand the downstream tubular opening defined by said end portions,

4. a spring retaining enlargement of the interior of said inner tubular member at the region of said slits and of greater transverse section than the unexpanded downstream tubular opening defined by said end portions, and

5. a backfire control valve seat defining a second orifice upstream of said slits and of smaller transverse section than said unexpanded downstream opening,

C. providing valve means having 1. a downstream metering portion dimensioned to move axially in a downstream direction within said metering orifice to restrict the same,

2. an upstream backfire valve portion dimensioned to seat at said backfire control valve seat to close said second orifice and to pass axially through said unexpanded downstream opening, and

3 a radial spring retaining shoulder between said metering portion and backfire valve portion,

D. providing a coil spring adapted to fit around said valve means downstream of the latters shoulder, having 1. a major portion dimensioned to pass freely into said inner member through said unexpanded downstream opening,

2. an upstream end of said major portion dimensioned to seat at said shoulder to resist downstream movement of said valve means, and

3. a downstream end of said spring enlarged with respect to said major portion and to said unexpanded downstream opening and dimensioned to fit snugly within said spring retaining enlargement,

E. assemblying said spring and valve means within said inner member with said upstream backfire valve portion confronting said backfire control valve seat and with said spring coiled around said valve means upstream of said spring retaining shoulder by l. inserting said spring and valve means through the downstream opening of said inner member,

2. inserting said enlarged downstream end of said spring into said spring retaining enlargement by flexing said downstream end portions to expand the downstream opening defined thereby, thereafter F. releasing the flexed downstream end portions of said inner member to their unflexed condition to confine said enlarged end of said spring within said spring retaining enlargement, and thereafter G. telescoping the downstream end of said inner member,

with said valve means and spring assembled therein, into the upstream end of said outer member.

7. In the method according to claim 6, the step of providing said inner tubular valve housing member comprising molding the same as a one-piece unit with a cylindrical passage downstream of said backfire control valve seat adapted to receive the major portion of said coil spring freely and having said interior spring retaining enlargement comprising a peripheral groove, and the step of providing said spring comprising the forming of said spring with a downstream coil having a coil diameter greater than the coil diameter of said major portion and dimensioned to be confined snugly within said groove. 

1. In a crankcase ventilating device for controlling the flow of gases from the crankcase to the fuel-air inlet induction conduit of an internal combustion engine to effect a predetermined low rate of flow when a predetermined large pressure differential exists between said crankcase and conduit corresponding to engine operation approximating idle conditions and to effect an increasing rate of flow when said pressure differential decreases with increasing engine load, the combination of A. a tubular valve housing comprising inner and outer tubular members having a gas passage extending therethrough and opening at upstream and downstream ends respectively adapted for connection with said crankcase and conduit respectively, B. said outer member defining a metering orifice comprising part of said passage, C. said inner member comprising a spring retainer of resilient material having
 1. a downstream end telescoped into the upstream end of said outer member,
 2. means effective before said inner member is telescoped into said outer member to permit radially outwardly resilient flexing of the downstream end portions of said inner member around the downstream opening defined thereby to expand said downstream opening to receive therethrough resilient means oversize with respect thereto, comprising a plurality of peripherally spaced and axially extending endwise opening slits in said downstream end of said inner member,
 3. an enlargement, with respect to its unexpanded downstream opening of its interior passage, at the region of said slits, and
 4. a backfire control valve seat defining a second orifice smaller than said unexpanded downstream opening and comprising a part of said passage upstream of said slits, D. valve means in said passage having
 1. a downstream metering portion movable in the downstream direction to restrict said metering orifice, and
 2. an upstream backfire valvE portion oversize with respect to said second orifice and movable in the upstream direction into seating engagement with said backfire control valve seat to close said passage, E. resilient means within said inner member for yieldingly opposing downstream movement of said valve means having
 1. one end seated on said valve means, and
 2. a second end oversize with respect to said unexpanded downstream opening of said inner member confined within said enlargement of the interior thereof to maintain a predetermined spatial relationship between said resilient means and inner member for all positions of said valve means.
 2. means effective before said inner member is telescoped into said outer member to permit radially outwardly resilient flexing of the downstream end portions of said inner member around the downstream opening defined thereby to expand said downstream opening to receive therethrough resilient means oversize with respect thereto, comprising a plurality of peripherally spaced and axially extending endwise opening slits in said downstream end of said inner member,
 2. an upstream backfire valvE portion oversize with respect to said second orifice and movable in the upstream direction into seating engagement with said backfire control valve seat to close said passage, E. resilient means within said inner member for yieldingly opposing downstream movement of said valve means having
 2. a second end oversize with respect to said unexpanded downstream opening of said inner member confined within said enlargement of the interior thereof to maintain a predetermined spatial relationship between said resilient means and inner member for all positions of said valve means.
 2. In a device according to claim 1, said inner member comprising an integral molded structure having a uniform interior cores section downstream of said second orifice except at said enlargement, said enlargement comprising an interior groove in said slit end, and said resilient means comprising a coil spring having a major portion freely movable axially within said inner member, said second end comprising an oversize coil of said spring adapted to pass through said downstream end upon outward flexing of said downstream end portions and dimensioned to fit snugly within said groove when said downstream end portions are unflexed.
 2. an upstream backfire valve portion oversize with respect to said second orifice and movable in the upstream direction into seating engagement with said backfire control valve seat to close said passage, E. resilient means within said inner member for yieldingly opposing downstream movement of said valve means having
 2. a second end oversize with respect to said downstream opening of said inner member confined within said enlargement of the interior thereof to maintain a predetermined spatial relationship between said resilient means and inner member for all positions of said valve means.
 2. means effective before said inner member is telescoped into said outer member to facilitate insertion of oversize resilient means into said inner member through the latter''s downstream opening comprising a plurality of peripherally spaced and axially extending endwise opening slits in said downstream end of said inner member,
 2. a metering orifice intermediate its ends, and
 2. a downstream end portion of cylindrical exterior section adapted to telescope snugly into said upstream end portion of cylindrical section,
 2. an upstream backfire valve portion dimensioned to seat at said backfire control valve seat to close said second orifice and to pass axially through said unexpanded downstream opening, and
 2. an upstream end of said major portion dimensioned to seat at said shoulder to resist downstream movement of said valve means, and
 2. inserting said enlarged downstream end of said spring into said spring retaining enlargement by flexing said downstream end portions to expand the downstream opening defined thereby, thereafter F. releasing the flexed downstream end portions of said inner member to their unflexed condition to confine said enlarged end of said spring within saiD spring retaining enlargement, and thereafter G. telescoping the downstream end of said inner member, with said valve means and spring assembled therein, into the upstream end of said outer member.
 3. a downstream end of said spring enlarged with respect to said major portion and to said unexpanded downstream opening and dimensioned to fit snugly within said spring retaining enlargement, E. assemblying said spring and valve means within said inner member with said upstream backfire valve portion confronting said backfire control valve seat and with said spring coiled around said valve means upstream of said spring retaining shoulder by
 3. a radial spring retaining shoulder between said metering portion and backfire valve portion, D. providing a coil spring adapted to fit around said valve means downstream of the latter''s shoulder, having
 3. a plurality of peripherally spaced and axially extending endwise opening slits in said downstream end portion to enable radial outward flexing of the downstream end portions between said slits to expand the downstream tubular opening defined by said end portions,
 3. an upstream end portion of cylindrical interior section, B. providing an inner tubular valve housing member having
 3. an enlargement with respect to said downstream opening of its interior passage at the region of said slits, and
 3. In the combination according to claim 2, said valve means having a shoulder downstream of said backfire valve portion thereof, said one end of said coil spring comprising the latter''s upstream coil seated on said shoulder, said oversize coil comprising the downstream coil of said coil spring.
 3. an enlargement, with respect to its unexpanded downstream opening of its interior passage, at the region of said slits, and
 4. a backfire control valve seat defining a second orifice smaller than said unexpanded downstream opening and comprising a part of said passage upstream of said slits, D. valve means in said passage having
 4. In a crankcase ventilating device for controlling the flow of gases from the crankcase to the fuel-air inlet induction conduit of an internal combustion engine to effect a predetermined low rate of flow when a predetermined large pressure differential exists between said crankcase and conduit corresponding to engine operation approximating idle conditions and to effect an increasing rate of flow when said pressure differential decreases with increasing engine load, the combination of A. a tubular valve housing comprising inner and outer tubular members having a gas passage extending therethrough and opening at upstream and downstream ends respectively adapted for connection with said crankcase and conduit respectively, B. said outer member defining a metering orifice comprising part of said passage, C. said inner member comprising a spring retainer having
 4. a backfire control valve seat defining a second orifice smaller than said downstream opening and comprising a part of said passage upstream of said slits, D. valve means in said passage having
 4. a spring retaining enlargement of the interior of said inner tubular member at the region of said slits and of greater transverse section than the unexpanded downstream tubular opening defined by said end portions, and
 5. a backfire control valve seat defining a second orifice upstream of said slits and of smaller transverse section than said unexpanded downstream opening, C. providing valve means having
 5. In the combination according to claim 4, said inner member comprising an integral molded structure having a uniform interior cross section downstream of said second orifice except at said enlargement, said enlargement comprising an interior groove in said slit end, and said resilient means comprising a coil spring having a major portion freely movable axially within said inner member, said second end comprising an oversize coil of said spring dimensioned to fit snugly within said groove.
 6. In the method of making a crankcase ventilating device for controlling the flow of gases from the crankcase to the fuel-air inlet induction conduit of an internal combustion engine to effect a predetermined low rate of flow when a predetermined large pressure differential exists between said crankcase and conduit corresponding to engine operation approximating idle conditions and to effect an increasing rate of flow when said pressure differential decreases with engine load, the steps of A. providing an outer tubular valve housing member having
 7. In the method according to claim 6, the step of providing said inner tubular valve housing member comprising molding the same as a one-piece unit with a cylindrical passage downstream of said backfire control valve seat adapted to receive the major portion of said coil spring freely and having said interior spring retaining enlargement comprising a peripheral groove, and the step of providing said spring comprising the forming of said spring with a downstream coil having a coil diameter greater than the coil diameter of said major portion and dimensioned to be confined snugly within said groove. 